1. Field of the Invention
This invention relates to nonwoven fabric suitable to throwaway use and particularly to a biodegradable nonwoven fabric which becomes extinct in the soil by microorganisms and to the molding vessel thereof.
2. Description of the Prior Art
Throwaway nonwoven fabrics typified by diapers are used in large quantities recently, because of their convenience. After use, however, they are treated as general wastes, and are disposed of by burning in an incineration site, because they are not decomposed in the soil and cause contamination of soil if used in reclamation. The increasing amount of use of the throwaway nonwoven fabrics is causing, therefore, a social problem such as damaged incineration furnaces and toxic exhaust gas, like other throwaway plastics.
In the field of agriculture and gardening, on the other hand, various materials are used for seedling mats and pots and planting mats. Rock wool, a mineral fiber, is used in large quantities because of its low price, hydrophilic nature, and adequate porosity. However it can be used only in the form of sheet, lacking moldability, and cannot be decomposed by microorganisms in the soil.
Pulp regenerated from old paper is cheap and excellent in hydrophilicity and water retentivity and is processed in the form of sheet and pot, but the decomposition of pulp is inhibited by the lignin contained in the pulp. In addition, lignin and a toughening agent such as acrylic amide naturally contained in the old paper are accumulated in the soil causing soil contamination. To solve these defects, cellulose based fabrics containing a smaller amount of lignin such as cotton and rayon, needle punched nonwoven fabrics, water needle punched nonwoven fabrics, etc, are used in the agricultural, gardening, and civil engineering fields. These fiber aggregates are completely decomposed by the microorganisms in the soil in periods of 1-3 days and produces no soil contamination, but can only be used generally in the form of sheet limited in use. In a special case, it is sewed into bag form, but is expensive. Also, it is impossible to disintegrate these materials by natural decomposition and finally must depend on incineration.